Fluid catalytic cracking (FCC) is a well known process for the conversion of relatively high boiling point hydrocarbons to lighter hydrocarbons. In many catalytic cracking reactors, often referred to as riser reactors or risers, e.g., vertical pipe reactors, a relatively long chain hydrocarbon feedstock, e.g., crude oil feedstock, reacts in contact with a catalyst to produce shorter chain products and spent catalyst (e.g., catalyst particles covered with coke). This process can be referred to as cracking the feed. The feedstock and fluidized catalyst are introduced at a lower entrance to the vertical riser, and travel vertically upwards within the riser reacting at very high temperatures until reaching an upper exit. The riser is often internally lined to minimize heat loss and resist erosion and/or corrosion.
Reaction efficiency in the riser depends, among other factors, on good (e.g., plug flow) and uniform mixing between the vaporized feedstock and fluidized catalyst. It is desirable that the feedstock be uniformly dispersed in a stream of fluidized catalyst that is moving up the riser. In many risers, however, even if near uniform dispersion is achieved at the riser entrance (feed contacting point), non-uniform mixing can occur as the materials travel upwards due, at least in part, to non-uniform cross-sectional gas velocities that result from temperature differentials, frictional drag, solid density gradients, and other factors. In some risers, for example, the upward velocity of the feedstock is lower near the riser wall and higher near the center. This non-uniform velocity profile may be referred to as reactor slip. Under such conditions, more dense fluidized catalyst tends to concentrate near the wall in the slower moving feedstock. This leads to uncontrolled mixing of the feed and catalyst which results in lower reaction efficiency and yield.
Attempts have been made to improve mixing along the vertical flow path of the riser. For example, obstacles such as baffles or other contact devices have been proposed to create turbulence and redirection of flow to cause more uniform mixing in the riser. Unfortunately, implementing and maintaining baffles in risers, which are typically relatively tall, e.g., heights of 10 to 50 meters (m), and narrow, e.g., internal diameters of 1 to 4 m, is difficult in general and is particularly problematic in retrofit situations in which the riser must be cut for access and erosion must be controlled downstream of the baffles. Additionally, safely removing and replacing baffles in risers, for example, during shutdown and/or maintenance of the riser is also problematic due to poor access to the internal riser which results in a prolonged maintenance time requirement.
Accordingly, it is desirable to provide apparatuses and risers for reacting a feedstock in the presence of a catalyst and methods for installing baffles in such risers with improved implementation of the baffles to increase reaction efficiency and valuable product yield. Additionally, it is desirable to provide methods for installing baffles in risers in which the baffles are relatively easy to remove and replace, for example, during shutdown and/or maintenance of the risers. Moreover, it is desirable to have the baffle completely shop fabricated and cured such that there is no field construction or maintenance and repairs required in the riser (at site). Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.